The present invention relates to a line voltage adapter for a thermostat of a type for receiving an extremely wide range of input voltages.
It has been known in the art to require thermostat control of a wide range of devices with widely variable operating voltages, at 60 Hz in the United States and 50 Hz in Europe or other locations. An attempt in the prior art to deal with the problem of arranging separate low and higher voltage devices is described in U.S. Pat. No. 5,592,989, wherein is described a circuitry and assembly for location of a voltage control device. An electronic thermostat having high and low voltage control capability and varied functional capabilities. The thermostat is particularly suited for use with fan coil heating and cooling units. Specifically the thermostat uses relays to actuate external devices such as heating and cooling equipment, fans and dampers. The use of relays permits control voltages for these external devices to be different (e.g. 24 VAC, 208-230 VAC or 277 VAC).
Overriding the circuit design considerations to accomplish the goal of wide range voltage adaptation are the Underwriter Laboratories' ratings requirements relating to heat transfer, fire resistance and pull strength for wire connections. Regardless of the design and configuration of the potentially several separately powered units related to control space heating and cooling, a thermostat is necessary to control the operation of each unit separately. Because of the varied operational characteristics that are possible, a single thermostat design has heretofore not been available which can operate the entire spectrum of the separate devices or units that are commercially available. It is known that because of the different operating voltages that are available, Underwriter Laboratories compliance specifications have resulted in thermostats being separated from control relays and the like, and this has caused increased costs to users because of the necessity for installing switches, relays and associated controls that are separated from the thermostat.
Accordingly, it is a primary object of the present invention to provide an improved voltage adapter for a thermostat for controlling heating and cooling related equipment with the widest range of voltages and with respect to the two primary available line frequencies at 50 and 60 Hz. It has been heretofor unknown to combine such advantages in a single voltage adapter unit which is incorporable into or next to the housing of the thermostat.